In the prosthetic dentistry, the reproduction of the color and transmittance is a key parameter on determining the property of prosthesis and teeth. Before coloring, the color of zirconia ceramics per se generally is white to ivory. Though such a color can easily simulate the color of natural teeth, it is still not sufficient to meet the requirements for the color of the prosthesis in clinical. The clients are satisfied, only after adjusting the color and the transmittance of zirconia per se to be similar to those of the teeth to be repaired. One of the most important principles in the prosthetic dentistry is to obtain a combination of the mechanical property and aesthetics with the proviso that the tissue of teeth can be maintained as much as possible. After coloring, if the zirconia-based dental corona can show a color and lustre similar to that of natural teeth, the thickness of the veneering porcelain can be reduced or the veneering porcelain can be completely avoided in the process of preparing the prosthesis without losing the idea aesthetics, meanwhile the amount of the tissue removed for the teeth can be reduced, thus more tissue of the dental can be maintained.
Up to now, there are mainly two methods for coloring the zirconia prosthesis: one method is adding the coloring agent into the zirconia powder, preparing a colored green body from the colored zirconia powder, and then machining and sintering, to obtain a prosthesis having a color similar to that of natural teeth. The other method is formulating a specific coloring solution, soaking the machined and not colored zirconia-based dental corona in the coloring solution for a given period, e.g., several minutes, or brushing the coloring solution on the zirconia prosthesis, and then sintering to obtain a prosthesis having a color similar to that of the natural teeth.
WO2009/014903 (also published as CN 101778807 A) disclosed a coloring solution for coloring dental ceramics, the solution comprising a solvent and coloring agents. The coloring agents contain rare earth metals and transition metals or ions thereof. The concentration of the rare earth metals or ions thereof in the solution is from about 0.05 to about 1 mole/liter solvent. The concentration of the transition metals or ions thereof in the solution is from about 0.00001 to about 0.05 mole/liter solution. In this patent application, the dental ceramic is colored by the coloring solution so that a color similar to that of natural teeth is obtained. However, this patent application did not mention the adjustment of the transmittance of dental ceramics.
WO2004/110959 (also published as CN 1805913 A) disclosed a coloring solution for coloring the ceramic frameworks, the ceramic framework colored by the coloring solution and a method for obtaining a uniformly colored ceramic framework. The solution comprises solvent, metal salts and polyethylene glycol having a molecular weight Mn of 1000 to 200000, wherein the metal salts comprise rear earth metal and transition metal ions. The application also focused on the color adjustment of the ceramic frameworks, and did not mention the adjustment of the transmittance of the ceramic frameworks. The main principle of this application is preventing the metal ions from diffusing from the interior of the ceramic frameworks to the surface thereof by utilizing the polyethylene glycol having a molecular weight Mn of 1000 to 200000.
Merely adjusting the dental ceramic prosthesis to be similar to that of the natural teeth can not make the prosthesis having aesthetics effects of truly simulating the natural teeth. The inventors of the present invention found that to achieve the aesthetics effects of truly simulating the natural teeth, in addition to the color, the transmittance of the prostheses also need to be adjusted. Thus, there is a need for a dental prostheses of ceramics that has aesthetics effects of truly simulating the natural teeth. To this end, the present invention provides a coloring solution for dental ceramics, when applying to the dental zirconia ceramics, a dental zirconia ceramic having good color and transmittance can be obtained, and thus aesthetics effects of truly simulating the natural teeth can be achieved.